Anisotropic Rock Poroelasticity Evolution in Ultra-low Permeability Sandstones under Pore Pressure, Confining Pressure, and Temperature: Experiments with Biot's Coefficient

This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure, confining pressure, and temperature. Several groups of experiments examining Biot's coefficient under different conditions were carried out. Results showed that Biot's coefficient decreased with increased pore pressure, and the variation trend is linear, but the decreasing rate is variable between materials. Biot's coefficient increased with increased confining pressure; the variation trend is linear, but the increasing rate varies by material as well. Generally, Biot's coefficient remains stable with increased temperature. Lithology, clay mineral content, particle arrangement, and pore arrangement showed impacts on Biot's coefficient. For strong hydrophilic clay minerals, expansion in water could result in a strong surface adsorption reaction, which could result in an increased fluid bulk modulus and higher Biot's coefficient. For skeleton minerals with strong lipophilicity, such as quartz and feldspar, increased oil saturation will also result in an adsorption reaction, leading to increased fluid bulk modulus and a higher Biot's coefficient. The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery (EOR) process.

Automated summary

This study demonstrated the evolution of anisotropic poroelasticity in ultra-low permeability reservoirs under different conditions. The Biot's coefficient was found to decrease with increased pore pressure and increase with increased confining pressure, while remaining stable with increased temperature. Factors such as lithology, clay mineral content, particle arrangement, and pore arrangement were shown to impact the Biot's coefficient. The study's findings provide valuable insights for enhancing oil recovery processes.